1. Field of the Invention
The present invention relates to a film forming method and a film forming apparatus for forming a thin film on a processing target such as a semiconductor wafer.
2. Description of the Related Art
In general, in order to manufacture a semiconductor integrated circuit, various processes such as a film forming process, an etching process, an oxidation process, a diffusion process, a surface modification process, a removal process of a natural oxidation film, and the like are performed on a semiconductor wafer formed of a silicon substrate or the like. The above processes may be performed in a single-wafer type processing apparatus that processes wafers one-by-one, or in a batch type processing apparatus that may process a plurality of wafers at once. For example, when the above processes are performed in an elongated, so-called batch type processing apparatus, semiconductor wafers are transferred from a cassette that can accommodate a plurality of semiconductor wafers, for example, 25 semiconductor wafers, to an elongated type wafer boat to be supported by the wafer boat in multiple stages.
On the wafer boat, for example, about 30 to 150 wafer sheets, the number of which may vary depending on sizes of the wafers, may be placed. The wafer boat is carried (loaded) in a processing container that can be exhausted, from a lower portion of the processing container, and the inside of the processing container is hermetically maintained. In addition, a predetermined heat treatment is performed while controlling various processing conditions such as a flow rate of a processing gas, a processing pressure, a processing temperature, and the like.
Here, as one of the factors for improving characteristics of a semiconductor integrated circuit, it is important to improve characteristics of an insulating film in the integrated circuit. In general, SiO2, phosphosilicate glass (PSG), plasma silicon oxide (P—SiO), plasma silicon nitride (P—SiN), spin on glass (SOG), Si3N4 (silicon nitride film), or the like is used as the insulating film in the integrated circuit. In addition, the silicon nitride film, in particular, is generally used for various uses because an insulating characteristic of the silicon nitride film is superior to that of a silicon oxide film, and the silicon nitride film may sufficiently function as an etching stopper film or an interlayer insulation film.
In addition, recently, demands for developing low-k circuit devices and for improving resistance against etching have increased greatly in order to improve characteristics of a circuit device (here, k is dielectric constant). Under these circumstances, since an aimed treatment may be performed without exposing the wafers to such a high temperature in the elongated, so-called batch type processing apparatus, a method of repeatedly forming films of a single layer to a few layers at the atomic level or films of a single layer to a few layers at the molecular level while intermittently supplying a raw material gas has been suggested. The above film forming method is generally referred to as an atomic layer deposition (ALD) method.
For example, Patent Reference 1 discloses a film forming method for forming a film of a laminate structure of multiple layers by stacking silicon nitride (SiN) thin films and boron nitride (BN) films alternately in multiple layers by using a remote plasma atomic layer deposition (RP-ALD) method. In addition, Patent Reference 2 discloses a film forming method for forming a SiCN film by using an ALD method, in which carbon (C) that is useful for improving an etching resistance is added in a silicon nitride film through a heat treatment in order to achieve a low-k characteristic and to improve the etching resistance.
However, although the above-described silicon nitride-based insulating films are low-k insulating films and have superior resistance against an etching process compared to conventional insulating films formed as silicon nitride films, they still don't obtain required properties. In particular, a property with respect to a leak current in an insulating film is not enough.